The Indian Journal of Tuberculosis - LRS Institute of Tuberculosis ...

10 A.K. CHAKRABORTYET AL
statements on the nature of working systems,
without resorting to the rigors of obtaining
statistical support from co-efficients of the effectvariables.
Others like to limit the number of
variables to be studied, or further verify whether
the nature of the findings generated by the model
are in consonance with a prior hypothesis. In
other words, the bounds of direct observation are
sought to be extended through constructing
models. The present study is an attempt on
similar lines. Its aim is to present the decision
makers a choice in selecting one among the
several alternative courses, worked out by an
interplay of several sets of variables that could
not have been practicably obtained from
observational studies.
The data from several relevant operational
studies have been used by us in seeking to
investigate the role of case-finding and treatment
under DTP, at various efficiency levels in the
context of tuberculosis control, consequent to the
introduction of SCC. The model thus constructed
could also be used to compute expectations,
based on the performance of some of the key
activities in tuberculosis control at some
hypothetically imputed levels, based on user
response and service efficiency. These
expectations, on the other hand, could also set the
process of matching the current as well as future
performance of DTP, subject to input variations
from time to time.
Material and Methods
The model was constructed on a Personal
Computer (PC-XT, ET&T), using LOTUS 1-2-3
software package. The operational flow chart
considered for the preparation of the model is
given in the Figure (P. 11). The definitions used
and the ratios and assumptions governing the
flow of events in the model, along with the
computed absolute numbers constituting the flow
are as follows :
Prevalence of cases in an average district: (A in
Fig.) The population size of an average Indian
district is taken as 1.5 million. The prevalence of
sputum culture positive cases among those aged
= >5 years in an average district works out to
5,000, at nearly 4/1,000 (Ref. 6). Case load for
an average DTP : (B in Fig.) The
case load in an average DTP is the number of
previously undiagnosed symptomatics reporting
to DTP units and diagnosed as cases. It is
calculated to be approximately 2,500 cases i.e.,
50% of the prevalence in the district 7
Potential of case-finding : (C in Fig.) It is the
number of cases, diagnosable by Ziehl-Neelsen
microscopy 8 , being 80% of 2,500 culture positive
case load i.e., 2,000 cases. These cases are taken
to be smear as well culture positive.
Efficiency of case-finding : (CF efficiency-D in
Fig.) It is the number or proportion of cases that
could be diagnosed out of previously undiagnosed
sputum smear positive cases presenting
themselves for diagnosis in a DTP. [At the
average level of efficiency of 33%, as estimated by
the Monitoring Section of National Tuberculosis
Institute, Bangalore 9 (NTI), about 660 cases].
Levels of compliance : These are the proportions
of doses taken (collected doses are presumed to
have been consumed) out of the total due by the
cases put on treatment. The levels of compliance
for INH-Thiacetazone regimen for standard
chemotherapy 10 (SR) and fully self administered
2ERH/4H2R2 SCC regimen 11 have been
considered for developing the model. These
regimens were selected because valid data on
compliance levels could be computed from them.
The levels of compliance for treatment are
defined as follows:
In respect of SR—expressed as percent of
collections made out of due in one year :
Level 1-up to 25; Levels 2-from 26 to 50;
Levels 3-from 51 to 75; Level 4-from 76 to 100.
In respect of SCO-expressed as percent of
drug collections during the first two months of
intensive and the following four months of
continuation phase:
Level 1-less than 80 in both intensive and
continuation phase; Level 2- less than 80 in
intensive phase and more than 80 in continuation
phase; Level 3-more than 80 in intensive phase
and less than 80 in continuation phase; Level 4-
more than 80 in both the phases. Rate of
Compliance: It is the proportion of cases who
take treatment at a given level of compliance
(Tables 1 and 2). These proportions are taken
from some operational studies and then rounded
off to the nearest digit in Tables 5 & 6 10 ' 11